Well you said "Christians" plural, I can tell you what I (and many) understand the word to mean, but on account of semantic differences, and various other complications, I cannot speak for every Christian.
That's fine, I don't expect you to. I'll be happy just to hear what you think.
"Prayer" refers to a state of communication or communion with God. In our world view God is a constant, and someone somewhere is at all times in said state. As a result, it is hard to respond to a question "What if God did not answer any prayers", because "answer" is not really a relevant word.
So your answer might be "nothing would happen if God stopped answering prayers, because he wasn't doing that anyway". Fair enough. But let's expand the question to deal with your particular circumstances. You believe that you are in communion with God when you pray. How do you experience this communion?
The dictionary defines communion as:
"
The sharing or exchanging of intimate thoughts and feelings, especially when the exchange is on a mental or spiritual level."
Does God share His thoughts and feelings with you as you pray? That sounds like it would certainly be noticeable if it ceased.
So, adapting the question: if praying no longer meant communion with God, what would you expect to happen? Would you notice the difference? How?
It is often mistakenly understood to be "talking to God and asking Him for something", sometimes even by Christians, but that is inaccurate. The dictionary is not very clear about it, I assume on account of attempting to include all religions, and avoid statements no one can prove.
I have to say, from my experience of Christians, that many, many Christians, quite possibly most of them, and at the very least a significant minority,
do think of prayer as talking to God and asking Him for things. As evidence of this, I offer
The Prayer Wall on this very forum. As you can see, it's a very busy part of Christian Forums, full of people asking for prayers for very specific things, and full of people answering and giving their prayers. On the front page as I write, there are prayers for a mosquito bite, global safety from the Corona virus, thyroid cancer, "my wife's salvation, and so on.
And if I may say so, this makes sense. The Christian religion teaches that God can and does work miracles in response to prayers. So whether your wife is dying of an incurable illness, or you've lost your car keys, doesn't it makes sense that you'd ask God for help?
You are incorrectly assuming the comments from Christians necessitate you specifically being "prayed for". You live in a world that is "prayed for" that is a certainty.
But that raises some interesting questions. If the whole world is being prayed for, then why am I living such a good life, and why are others living such terrible lives? Besides which, I don't think this issue is really something that you and I should be talking about, because it was raised in response to a person who seems to think that terrible things will happen to me if people stop praying, and I understand that you don't believe this.